Dispensers for disseminating a volatile substance such as perfume, fragrance, incense, deodorant, disinfectant, medicated liquid, germicide, or insecticide have been known. These devices disguise, remove or create an odor or aroma. Andeweg, in U.S. Pat. No. 3,948,445 issued Apr. 6, 1976, discloses a combination air freshening device and night light. Andeweg's devices are illustrated in FIGS. 1, 2A, and 2B. As shown in FIG. 1, Andeweg's device has an electric plug base 1 with electric plug prongs 2 for inserting into a wall electrical receptacle or outlet. The base 1 mounts a light bulb 3 that is a source of both light and heat. Side walls 4, 5 and 6 are scent, air freshener and/or insecticide substance impregnated material walls subject to controlled release of vapor with the heating from light bulb 3. Andeweg also discloses the device of FIG. 2A which includes a base 11 with electric plug prongs 12 for plugging in a wall electrical receptacle or outlet and an electrical bulb socket into which the base of electric light bulb 13 is threaded. An open top container 14 of glass is held in place between the top of the base 11 and the base of the light bulb 13. A reservoir material 15 such as scented wax is placed in the cupped container 14. As shown in FIG. 2B Andeweg provides a device with a base 21 with electric plug prongs 22 and an electrical bulb socket into which the threaded base of electric light bulb 23 is threaded. A reservoir material 25 such as scented wax is placed between an outer container 24 and an inner container 26 above a spacer element 27.
A more recent development provides for a plug-in volatile substance dispenser as shown in FIGS. 3A and FIG. 3B. This dispenser has a base 31 with electric plug prongs 32 insertable into a wall electrical receptacle or outlet. Fuse links 34 distribute electricity to a screen printable film, fixed resistor heat pad 33 which is supplied with a thermal coating that encapsulates the electrical components and provides even heat distribution over the resistor heat pad 33. Alternatively, the resistor heat pad and thermal coating may be replaced with a chip resistor (not shown) with wires for connecting to the fuse link. A volatile substance is provided in absorbent substrate 35. Cover 36 has openings to permit the volatile substance to diffuse into the atmosphere. An impermeable film 37 covers the openings in cover 36 until the film is removed prior to use. In this dispenser, the resistor heat pad 33 or chip resistor is the source of heat for vaporizing the volatile substance.
It is known to view the volatile substance in a dispenser to determine if it is used up as in the Andeweg air freshener, discussed above and in Martens et al., U.S. Pat. No. 4,583,686 issued Apr. 22, 1986. Simply viewing the volatile substance to determine if it is used up is not possible if the volatile substance is impregnated in an absorbent material.
Elsner U.S. Pat. No. 3,780,260 issued Dec. 18, 1973, discloses a combination night light and liquid vaporizer wherein an electric lamp provides a heat source for vaporizing the liquid in the container as well as illumination for the night light. The lamp is controlled through an energizing circuit which includes an electric flow path through the vaporizable liquid between spaced electrodes built into the container. As soon as the level of the vaporizable liquid is reduced to an amount such that the circuit energizing the lamp is cut off, the lamp turns off. Hence, the Elsner night light and vaporizer detects the absence of the vaporizable liquid. The circuit, however, requiring a vaporizable liquid which permits electrical energy to flow between electrodes is rather complicated and not particularly reliable. The volatile substance must be a liquid.
There is, therefore, a need for a volatile substance dispenser and night light which provides an indication of the dissipation of the volatile substance without close inspection of the device to see if the volatile substance is gone or if a sufficient amount of the substance remains to be effective. Further, there is a need for a night light/volatile substance dispenser which is simple in construction and use and indicates the dissipation of the volatile substance if the substance is in a form such as impregnated in an absorbent material where dissipation cannot be readily determined by viewing the absorbent material. There is further a need for a night light/volatile substance dispenser which indicates dissipation of the volatile substance without complicated and unreliable detection of the volatile substance or unreliable circuit components such as electrodes. There is further a need for a night light/volatile substance dispenser which indicates the dissipation of the volatile substance although the volatile substance is not a liquid which permits electrical energy to flow through it.